[CN-1303]: add env var docs (#209)

docs/modules/ROOT/examples/env-vars.yaml

@@ -0,0 +1,20 @@
+apiVersion: hazelcast.com/v1alpha1
+kind: Hazelcast
+metadata:
+  name: hazelcast
+spec:
+  clusterSize: 3
+  repository: 'docker.io/hazelcast/hazelcast-enterprise'
+  env:
+    - name: ENVIRONMENT
+      value: PROD
+    - name: AWS_ACCESS_KEY_ID
+      valueFrom:
+        secretKeyRef:
+          name: aws-secret
+          key: AWS_ACCESS_KEY_ID
+    - name: AWS_SECRET_KEY
+      valueFrom:
+        secretKeyRef:
+          name: aws-secret
+          key: AWS_SECRET_KEY

docs/modules/ROOT/nav.adoc

@@ -22,6 +22,7 @@
 * xref:high-availability-mode.adoc[High Availability Mode]
 * xref:native-memory.adoc[Native Memory]
 * xref:jvm-parameters.adoc[Configuring JVM Parameters]
+* xref:env-vars.adoc[Configuring Environment Variables]
 * xref:resource-configuration.adoc[Configuring Resource Limits]
 * xref:hazelcast-parameters.adoc[Configuring System Properties]
 * xref:advanced-networking.adoc[Advanced Networking]

docs/modules/ROOT/pages/env-vars.adoc

@@ -0,0 +1,5 @@
+= Configuring Environment Variables
+
+You can configure the environment variables in the `hazelcast` pods using the `env` field of the CRD spec. `env` field supports the same format with link:https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.27/#envvar-v1-core/[Kubernetes' EnvVar format].
+
+WARNING: You cannot use the `env` field to configure Hazelcast environment variables, which are prefixed `HZ_`. To configure the Hazelcast environment variables, use xref:custom-config.adoc[Custom Config].